Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!mit-eddie!uw-beaver!uw-june!moore
From: moore@cs.washington.edu (Charles Moore)
Newsgroups: comp.sys.mac.hypercard
Subject: Re: Intercepting deleteCard message
Summary: on doMenu
Message-ID: <12568@june.cs.washington.edu>
Date: 17 Jul 90 21:16:36 GMT
References: <6057@bgsuvax.UUCP>
Organization: U of Washington, Computer Science, Seattle
Lines: 36

In article <6057@bgsuvax.UUCP>, instone@bgsuvax.UUCP (Keith Instone) writes:
> I can keep the user from sorting my stack with this simple little
> handler:
>         on sort
>         end sort
> 
> but this doesn't work for the deleteCard message (that is, the empty handler
> doesn't keep the card from getting deleted).
> 
> All I REALLY want to do is ask "Are you sure you want to delete this card?"
> and abort if the user says NO.

The deleteCard message is NOT the message that causes HyperCard to delete
the card.  Rather, deleteCard gets sent to a card that is about to be
deleted just prior to its deletion.  This allows some handler to recognize
that a deletion is about to occur and do something appropriate.  The
HyperCard Script Language Guide explains this and other purely informational
system messages.

What you want is:

on doMenu theCommand
  if theCommand is "Delete Card" then
    answer "Are you sure you want to delete this card?" with "OK" and "Cancel"
    if it is "OK" then
      pass doMenu
    end if
  else
    pass doMenu
  end if
end doMenu

Note: The "else pass doMenu" part is VERY important.  If you don't include
it, you will suddenly discover that none of your menu commands work.

Charles Moore